FIG. 1 shows such an example of a projection exposure system 1 that includes an illumination apparatus 3 and an apparatus 4 to accommodate and position a mask provided with a grid-like structure, a so-called reticle 5, by which the subsequent structures on a wafer 2 are determined. Projection exposure system 1 also includes an apparatus 6 to hold, move and position the wafer 2, and an imaging apparatus, namely a projection objective 7 having a plurality of optical elements, such as lenses 8 which are mounted in an objective housing 10 of the projection objective 7 via frames 9.
Typically, a basic functional principle in this case provides that the structures inserted into the reticle 5 are imaged reduced in size on the wafer 2. The illumination apparatus 3 provides a projection beam 11 of electromagnetic radiation for imaging the reticle 5 on the wafer 2, for example from the visible band, the UV or EUV band. A laser or the like can be used as a source of this radiation. The radiation is formed in the illumination apparatus 3 by optical elements such that the projection beam 11 has the desired properties with regard to diameter, polarization, shape of the wavefront and the like when it is incident on the reticle 5. The optical elements may be refractive, reflective, or different types of components, or combinations thereof.
Often, after exposure, the wafer 2 is moved on in the direction of the arrow, so that a multiplicity of individual regions, each having the structure prescribed by the reticle 5, are exposed on the same wafer 2. Due to the step-like feeding movement of the wafer 2 in the projection exposure system 1, it is often also referred to as a stepper. Optionally, a scanning image of each area is carried out in many modern machines, and such systems are commonly referred to as scanners.
An image of the reticle 5 is generated via the projection beam 11 and is transferred to the wafer 2 with a correspondingly reduced size by the projection objective 7, as already explained above. The projection objective 7 has a multiplicity of individual refractive, diffractive and/or reflective optical elements such as lenses, mirrors, prisms, end plates and the like.